Assessment of Fecal (Escherichia coli) contamination in Wild, Caged, and Market Fish (Nile Tilapia) from Selected Markets in Kisumu, Kenya

Fish is an essential source of animal protein in Kenya, playing a vital role in food security, nutrition, and economic livelihoods. The fisheries sector, while currently contributing about 0.8% to Kenya’s GDP, has significant potential for growth, especially through improved aquaculture and value addition. Nile tilapia (Oreochromis niloticus) dominates both aquaculture and wild catches from Lake Victoria, representing over 75% of aquaculture production. However, fish are highly perishable and vulnerable to microbial contamination at various stages, from harvesting to marketing. Escherichia coli (E. coli) is a key indicator of fecal contamination and food safety. Its presence in fish not only signals unsanitary handling but also the possible presence of other pathogens such as Salmonella, Shigella, and Vibrio species. In Kenya, diarrheal diseases are a major public health concern, especially for children, the elderly, and immunocompromised populations. This study focused on Kisumu County, a major hub for fish trade on Lake Victoria, and aimed to assess E. coli prevalence in fish from wild, caged, and market sources. A total of 104 O. niloticus fish samples were aseptically collected from the selected sources between November and December 2025. The samples were transported to the Kenya Marine and Fisheries Research Institute (KMFRI) microbiology laboratory for analysis. Results showed no E. coli contamination in wild-caught fish, indicating good source water quality. However, caged fish had a 31.1% contamination rate, with significant differences among cages (ranging from 6.7% to 53.3%), likely reflecting varying management practices. Fish from markets had the highest contamination, at 49.1%, with some markets such as Obunga showing 100% contamination of fried fish, while others like Star Market had zero contamination. These findings suggest that proper hygiene and management can reduce contamination. The study provides evidence-based recommendations for interventions across the supply chain to improve food safety in Kenyan fish markets nationwide.